NationStates Jolt Archive

You Can't Travel Back in Time, Scientists Say

Sara Goudarzi
LiveScience Staff Writer
LiveScience.comFri Mar 9, 8:10 AM ET

The urge to hug a departed loved one again or prevent atrocities are among the compelling reasons that keep the notion of time travel alive in the minds of many.

While the idea makes for great fiction, some scientists now say traveling to the past is impossible.

There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller, “The Elegant Universe” and a physicist at Columbia University.“And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it. Most of us think that almost all of them can be ruled out.”
Vote for Your Favorite Time Travel Tale

The fourth dimension

In physics, time is described as a dimension much like length, width, and height. When you travel from your house to the grocery store, you’re traveling through a direction in space, making headway in all the spatial dimensions—length, width and height. But you’re also traveling forward in time, the fourth dimension.

“Space and time are tangled together in a sort of a four-dimensional fabric called space-time,” said Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book “One Universe: At Home In The Cosmos.”

Space-time, Liu explains, can be thought of as a piece of spandex with four dimensions. “When something that has mass—you and I, an object, a planet, or any star—sits in that piece of four-dimensional spandex, it causes it to create a dimple,” he said. “That dimple is a manifestation of space-time bending to accommodate this mass.”

The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity.

Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn’t share this multi-directional freedom.

“In this four-dimensional space-time, you’re only able to move forward in time,” Liu told LiveScience.
Video: Can You Time Travel?

Tunneling to the past

A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole—a hypothetical tunnel connecting two regions of space-time. The regions bridged could be two completely different universes or two parts of one universe. Matter can travel through either mouth of the wormhole to reach a destination on the other side.

“Wormholes are the future, wormholes are the past,” said Michio Kaku, author of “Hyperspace” and “Parallel Worlds” and a physicist at the City University of New York. “But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today’s technology.”

To punch a hole into the fabric of space-time, Kaku explained, would require the energy of a star or negative energy, an exotic entity with an energy of less than nothing.

Greene, an expert on string theory—which views matter in a minimum of 10 dimensions and tries to bridge the gap between particle physics and nature's fundamental forces, questioned this scenario.

“Many people who study the subject doubt that that approach has any chance of working,” Greene said in an interview . “But the basic idea if you’re very, very optimistic is that if you fiddle with the wormhole openings, you can make it not only a shortcut from a point in space to another point in space, but a shortcut from one moment in time to another moment in time.”
Video: How to Time Travel!

Cosmic strings

Another popular theory for potential time travelers involves something called cosmic strings—narrow tubes of energy stretched across the entire length of the ever-expanding universe. These skinny regions, leftover from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.

Cosmic strings are either infinite or they’re in loops, with no ends, said J. Richard Gott, author of “Time Travel in Einstein's Universe” and an astrophysicist at Princeton University. “So they are either like spaghetti or SpaghettiO’s.”

The approach of two such strings parallel to each other, said Gott, will bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory.

“This is a project that a super civilization might attempt,” Gott told LiveScience. “It’s far beyond what we can do. We’re a civilization that’s not even controlling the energy resources of our planet.”

Impossible, for now

Mathematically, you can certainly say something is traveling to the past, Liu said. “But it is not possible for you and me to travel backward in time,” he said.

However, some scientists believe that traveling to the past is, in fact, theoretically possible, though impractical.

Maybe if there were a theory of everything, one could solve all of Einstein’s equations through a wormhole, and see whether time travel is really possible, Kaku said. “But that would require a technology far more advanced than anything we can muster," he said. "Don’t expect any young inventor to announce tomorrow in a press release that he or she has invented a time machine in their basement.”

For now, the only definitive part of travel in the fourth dimension is that we’re stepping further into the future with each passing moment. So for those hoping to see Earth a million years from now, scientists have good news.

“If you want to know what the Earth is like one million years from now, I’ll tell you how to do that,” said Greene, a consultant for “Déjà Vu,” a recent movie that dealt with time travel. “Build a spaceship. Go near the speed of light for a length of time—that I could calculate. Come back to Earth, and when you step out of your ship you will have aged perhaps one year while the Earth would have aged one million years. You would have traveled to Earth’s future.”
http://news.yahoo.com/s/livescience/20070309/sc_livescience/youcanttravelbackintimescientistssay

Well damn, there goes all that great Sci-fi.

Thoughts? And, if they are wrong and you COULD go back, what would you do?

I've heard before that no (hypothetical) time machine could take you back in time to before the machine itself existed.

Can't remember why. Science™, probably.

I would create some very clever photoshopped images of Adolph Hitler in compromising positions and performing odd sexual fetishes and deposit them into the hands of magazine and newspaper editors throughout the 20s and 30s.

Killing is so uncreative. :p

I would create some very clever photoshopped images of Adolph Hitler in compromising positions and performing odd sexual fetishes and deposit them into the hands of magazine and newspaper editors throughout the 20s and 30s.

Killing is so uncreative. :p

Robot Chicken has already beaten you to it. One of their eps show him giving a speech when the overhead tv screen gets overriden to show him on the toilet while suffering from diearhea.

Robot Chicken has already beaten you to it. One of their eps show him giving a speech when the overhead tv screen gets overriden to show him on the toilet while suffering from diearhea.

Curses! Foiled again! :mad:

None of the above makes terribly much sense to me. Assuming Greene and the rest of the famous gaggle are talking about time as laid out in relativity, wouldn't one have to deconstruct every event in the entire universe from the present to the destination point in the past? Time, after all, is a subjective orientation.

And even if one could do something like that, woulædn't it be a recreation of the past, rather than the actual past? - Not saying it makes any practical difference.

Unless there's an 'ether' I don't see how one'd be able to slog around in it.

http://i6.photobucket.com/albums/y223/GermanNightmare/DocBrown.jpg

_You've got to be kidding me!

This forum is perfect example of working time travel.:D

In other news, water is wet.

So, hold on: all we need to do it is just a lot of energy? Shit, I thought it was something actually difficult.

And only one star's worth at that...we could do that in fairly short order, maybe a century or two which is nothing on a human scale, let alone a galactic one. That's not going to be too tough, especially once we've got fusion or somehing like that.

Olmedreca;12422657']This forum is perfect example of working time travel.:DMaybe you could try to get in contact with whoever operates the universe and convince him to switch to jolt. Then just place yourself inside a large package, post it, and you'll arrive at your destination in the past.

http://www.toaster.org/images/homer_toaster.jpg

Crisis averted.

http://news.yahoo.com/s/livescience/20070309/sc_livescience/youcanttravelbackintimescientistssay

Well damn, there goes all that great Sci-fi.

Thoughts? And, if they are wrong and you COULD go back, what would you do?

Time Travel Made Easy:

1) Create a stable artificial wormhole
2) Move one end of the wormhole at or near the speed of light.
3) Time Travel!


Granted wormholes are theoretical, but still. Isn't time dilation fun?

In other news, water is wet.


but is it wet if u never touched it? prove it...

http://news.yahoo.com/s/livescience/20070309/sc_livescience/youcanttravelbackintimescientistssay

Well damn, there goes all that great Sci-fi.

Thoughts? And, if they are wrong and you COULD go back, what would you do?


Just because we can't do it currently doesn't mean it isn't possible, scientist have said that about alot of things that we now do, and take for granted in doing so. Even so I hope we will never discover how to travel in time, can you imagine a dictator or a terrorist that can travel back in time? :eek:

I've heard before that no (hypothetical) time machine could take you back in time to before the machine itself existed.

Can't remember why. Science™, probably.

Read a similar article in pop sci. Basic principle is that, were we to use wormholes, the earliest you could go back was the point in time when the wormhole formed.

http://i6.photobucket.com/albums/y223/GermanNightmare/DocBrown.jpg

_You've got to be kidding me!
Yes, Marty!

Ever get deja vu? :p

Read a similar article in pop sci. Basic principle is that, were we to use wormholes, the earliest you could go back was the point in time when the wormhole formed.

Of course, if the wormhole formed a really, really long time ago that could be pretty useful. Although personally I would think going forward in time would be more useful, it's probably not possible.

Just because we can't do it currently doesn't mean it isn't possible, scientist have said that about alot of things that we now do, and take for granted in doing so. Even so I hope we will never discover how to travel in time, can you imagine a dictator or a terrorist that can travel back in time? :eek:

I guess we'd need to train elite agents that would be specialized in eliminating "reality deviants" like that. Perhaps we could also use them for experiments in engineering the past, but that's just the technist in me speculating.

So this means NERVUN is actually going to have to pay the fines on those long-overdue library books, huh?

Of course, if the wormhole formed a really, really long time ago that could be pretty useful. Although personally I would think going forward in time would be more useful, it's probably not possible.

Yes, but these wormholes, in our theoretical models of them, have an extremely small lifespan. In order to have an effective time travel system you would need to keep both ends artificially somehow.

I never assumed it was possible (even though I'd love to be proven wrong). I always figured our future selves would have made contact with the present/ past; therefore we'd already know if it was possible.

I never assumed it was possible (even though I'd love to be proven wrong). I always figured our future selves would have made contact with the present/ past; therefore we'd already know if it was possible.

Maybe that's what UFOs actually are. :eek:

But then again, they'd also want to avoid interfering with the past for any number of reasons, so contact could be a monstrously bad idea for all involved.

Maybe that's what UFOs actually are. :eek:

But then again, they'd also want to avoid interfering with the past for any number of reasons, so contact could be a monstrously bad idea for all involved.

My theory is they'd interfere first, then realise it was a terribly bad idea. But then again I'm more than a little misanthropic.

Maybe they already have interfered. It's not like we would be able to tell, after all. :eek:

Well, if they would descend from their temporal vortex in a highly advanced timeship we probably would notice ;)

My theory is they'd interfere first, then realise it was a terribly bad idea. But then again I'm more than a little misanthropic.

Well, I imagine if you look at some historical events it's not hard to imagine inadvertent tinkering with the past. Of course, the problem is that we'll never know if it happens.

Maybe they killed Nikolai Tesla or something strange like that...

My theory is they'd interfere first, then realise it was a terribly bad idea. But then again I'm more than a little misanthropic.

Maybe they already have interfered. It's not like we would be able to tell, after all. :eek:

Yes, Marty!

Ever get deja vu? :p
I don't think so, but I could check with the kitchen.

I would create some very clever photoshopped images of Adolph Hitler in compromising positions and performing odd sexual fetishes and deposit them into the hands of magazine and newspaper editors throughout the 20s and 30s.

Killing is so uncreative. :p

I'm pretty sure this sort of thing happened in reality. They got some artist woman to deface pictures of Hitler. One had a picture of hitler with the slogan(in german) What we have, we hold, she altered it(sans photoshop) to have hitler shaking hands with little hitler.

Maybe they already have interfered. It's not like we would be able to tell, after all. :eek:

True enough. It hurts my head to think about it.

Theoretically "they" could go do some tinkering and inadvertantly set in motion a chain of events that would end with you never being born. :eek:

I didnt believe we could do it anyway.

You know how you have to use a huge surplus of energy to fight entropy and make energy go from the colder matter to the warmer matter, like we do in refrigerators and air conditioners?

Going BACK in time would be the same as fighting entropy. You´re fighting a natural law, and making it go backwards.

So, in my ignorant opinion, it would take like the energy from 500 billion atomic bombs to make the universe go back 1 second in time.

Now, if you could make it local, and make it affect only Earth, it could use much less energy, like 10 million bombs to make the Earth go 1 minute back.

Boo!
You win this round Science!

So, in my ignorant opinion, it would take like the energy from 500 billion atomic bombs to make the universe go back 1 second in time.

Well, you wouldn't be making the universe go back in time, you'd be using the energy to punch a hole in spacetime to go back in time.

But then again, we're better off planning where we're going to go once we reach the end of stellar formation and the possibility of some kind of universe death is a possibility. Of course, I think we can find somewhere else in the next 100 trillion years or so without difficulty. I mean, I kind of want to get out of here before the Big Rip/Crunch/Heat Death/Whatever ends this place.

Well, you wouldn't be making the universe go back in time, you'd be using the energy to punch a hole in spacetime to go back in time.

But then again, we're better off planning where we're going to go once we reach the end of stellar formation and the possibility of some kind of universe death is a possibility. Of course, I think we can find somewhere else in the next 100 trillion years or so without difficulty. I mean, I kind of want to get out of here before the Big Rip/Crunch/Heat Death/Whatever ends this place.

Getting a Spacetime Hole Puncher would sort humanity pretty permanently. It'd be kind of like "Feck the universe is gonna end next week." "Alright, everyone through the hole, you know the drill"

Well, you wouldn't be making the universe go back in time, you'd be using the energy to punch a hole in spacetime to go back in time.

But then again, we're better off planning where we're going to go once we reach the end of stellar formation and the possibility of some kind of universe death is a possibility. Of course, I think we can find somewhere else in the next 100 trillion years or so without difficulty. I mean, I kind of want to get out of here before the Big Rip/Crunch/Heat Death/Whatever ends this place.

Well, I know shit about physics, but I know about chemistry, and I do know matter doesnt reproduce itself.

So you really couldnt go back to another time without destroying the current time. You would have to transform it. Yes, it would take much less energy if you could directly transform the matter now in what it was 500, 1000 or 2.000.000 years ago. That would be ideal, because that way you would need the same ammount of energy to go back 1 year or 1 billion years.

But I dont see it like that. People believe there is some kind of universal information holder who, right now, has information on how the past was and the future will be. I think things are much more simple: things change due to certain laws, but the result is umpredictable. That means you cant know how the future will be, and the knowledge of how the past was is lost forever. So the only way to know how the past was, and make sure it becomes as it was before, you would have to reverse all natural and humans laws and make everything go backwards in a steady pace. From one second before to two seconds before. Until you reach the proper destination.

I see the idea of multiple universes as quite stupid. That is wishfull thinking. Or that there are infinite earths and that every nanosecond we go from one to the other, and that if you want to go back in time you just need to "transport" yourself to another universe/earth that exists in a time much more less developed than yours.

I do believe you can go forward in time, because it would take much less energy. It would be as easy as making sure your hand gets hot if you touch a warm metal bar. But going back in time would go so much against the natural laws of physics that you would need to use so much energy, something like we do in refrigerators and air conditioners.

Worm holes and black holes that take you to the past or future sounds like a lot of shit to me.

I guess we'd need to train elite agents that would be specialized in eliminating "reality deviants" like that. Perhaps we could also use them for experiments in engineering the past, but that's just the technist in me speculating.

sounds a bit like 'twelve monkeys'.

Right, the say they need the power of a star expolding. Or Something. When the sun blows up in god knows when, we'll have 8 minutes to harness the energy and go back like...4 days or something...

Im a little bit rusty on my astrophysics at current:rolleyes:

I guess we'd need to train elite agents that would be specialized in eliminating "reality deviants" like that. Perhaps we could also use them for experiments in engineering the past, but that's just the technist in me speculating.


Yea but who will decide who is a "reality deviant", and who is not? George W? God forbid!!!!!!

http://en.wikipedia.org/wiki/Novikov_self-consistency_principle

Scientists also warned about the health effects of going over 25 miles per hour when trains first came around.
And as I recall a number of scientists 'proved' that the sound barrier couldnt be broken without destroying the craft doing the breaking, or at all in some cases.
The point is...
Scientists fail sometimes.
Oh, and the universe doesnt run on math.

http://news.yahoo.com/s/livescience/20070309/sc_livescience/youcanttravelbackintimescientistssay

Well damn, there goes all that great Sci-fi.

Thoughts? And, if they are wrong and you COULD go back, what would you do?

be a soldier in the rome empire, WW1,WW2, korean war and nam

be a soldier in the rome empire, WW1,WW2, korean war and nam


Go back and change some of the stupid things I did earlier in my life. Also I would feel obligated to protect the people that " Vatalia " calls " Reality Deviants " from those who would come meaning to harm them to change the timeline in their favor. The second reason is why I developed time travel technology here in NS.

http://news.yahoo.com/s/livescience/20070309/sc_livescience/youcanttravelbackintimescientistssay

Well damn, there goes all that great Sci-fi.

Thoughts? And, if they are wrong and you COULD go back, what would you do?

If I could go back in time I'd go back to the very beginning of the Universe, killing myself and having my mere presence utterly change the way the Universe evolves.
On second thought, maybe not. Going back to a singularity would be painful...

Anyway...
On my thoughts of time travel.

One cannot alter the fabric of spacetime directly, no matter how much energy you have at your disposal. It's impossible.

However, one could do it with matter, in the form of a singularity.
Theoretically one could somehow alter the way a singularity (a singularity being a point of infinite space-time curvature, for non-physicists) was formed and have it exist in multiple times simultaneously (I actually wrote a short paper as to why that may actually be anyway; I'll see if I can find it somewhere, along with my other theories on the nature of the Universe); at the area around that singularity one would an area of space-time so 'twisted' that there would likely be minor or maybe major time anomalies there, including areas in which it was still the past.

Interestingly, I also once wrote a short article for my newsletter explaining why the past, present and future don't actually exist. I'll see if I can dig that out as well.

And before you ask: yes, I am a physicist. Not by career; that would be difficult at the age of 15. Merely by merit of understanding advanced concepts, doing my own research into them and being very interested in the subject as a whole.

Ilaer

If I could go back in time I'd go back to the very beginning of the Universe, killing myself and having my mere presence utterly change the way the Universe evolves.
On second thought, maybe not. Going back to a singularity would be painful...

Anyway...
On my thoughts of time travel.

One cannot alter the fabric of spacetime directly, no matter how much energy you have at your disposal. It's impossible.

However, one could do it with matter, in the form of a singularity.
Theoretically one could somehow alter the way a singularity (a singularity being a point of infinite space-time curvature, for non-physicists) was formed and have it exist in multiple times simultaneously (I actually wrote a short paper as to why that may actually be anyway; I'll see if I can find it somewhere, along with my other theories on the nature of the Universe); at the area around that singularity one would an area of space-time so 'twisted' that there would likely be minor or maybe major time anomalies there, including areas in which it was still the past.

Interestingly, I also once wrote a short article for my newsletter explaining why the past, present and future don't actually exist. I'll see if I can dig that out as well.

And before you ask: yes, I am a physicist. Not by career; that would be difficult at the age of 15. Merely by merit of understanding advanced concepts, doing my own research into them and being very interested in the subject as a whole.

Ilaer

Just out of curiosity, what's your definition of "advanced concepts"?

Just out of curiosity, what's your definition of "advanced concepts"?

Well, advanced for my age. For example, the concepts behind gravitational theory and that of the other forces, the implications of Heisenberg's Uncertainty Principle, Einstein's Theories of Relativity, string theory, and other such gewgaws.

Ilaer

Well, advanced for my age. For example, the concepts behind gravitational theory and that of the other forces, the implications of Heisenberg's Uncertainty Principle, Einstein's Theories of Relativity, string theory, and other such gewgaws.

Ilaer

Ah, ok. I would've been a little shocked to hear you claiming you knew and understood the math behind things like Quantum Mech. and Stat. Thermo. given that I'm 20 and struggling with both.

Ah, ok. I would've been a little shocked to hear you claiming you knew and understood the math behind things like Quantum Mech. and Stat. Thermo. given that I'm 20 and struggling with both.

No, but I'd sure like to! :D
As soon as I have the chance I'm buying more books about physics, especially covering that first subject. At the moment the only moderately serious book I own is Professor Stephen Hawking's 'A Brief History of Time', and thus I am forced to resort to the ever-unreliable internet for more knowledge.
Also, I have far too many Terry Pratchett books on my shelves. I need some way to let people know that I'm not stalking him.
Studying aspects of quantum physics would probably do the trick.

Ilaer

Well, if you believe in special relativity, then all you have to do is go faster than the speed of light, of course that's only a theory that hasn't been proven yet, but it is a theorized result.

And as for it being impossible to travel back in time, who's to say what is or isn't possible? If dimensional travel could be perfected, we could instantly stop moving in the acceleration plane and instead move in the velocity,position, and time planes which could allow us to gain light speed instantaneously.

I would create some very clever photoshopped images of Adolph Hitler in compromising positions and performing odd sexual fetishes and deposit them into the hands of magazine and newspaper editors throughout the 20s and 30s.

Killing is so uncreative. :p

I'd go back and show Hitler's father the Prince half-time show. Apparently that makes people gay. Problem solved. *nods*

Well, if you believe in special relativity, then all you have to do is go faster than the speed of light, of course that's only a theory that hasn't been proven yet, but it is a theorized result.

And as for it being impossible to travel back in time, who's to say what is or isn't possible? If dimensional travel could be perfected, we could instantly stop moving in the acceleration plane and instead move in the velocity,position, and time planes which could allow us to gain light speed instantaneously.

Possibly the most confusing post I've ever read.
I think you're suggesting a way to get around the problem of travelling faster than light by changing velocity instantly; a bit like going from A-Z in the alphabet without going through all the other letters first.
Am I right?
If so, then you mangled it a bit, especially by mentioning velocity and position planes and other such things.

Ilaer

2 separate ideas, the first was the idea for time travel, the second a way to achieve light speed without gaining infinite mass. Exclusivity of dimensions is the concept I forgot to mention, if it is possible, we can isolate one dimension from the others with few effects other than spontaneous time passage, but that should be negligible, a few seconds every day or so, but this is only to achieve light speed, at which point acceleration can be reintegrated.

as soon as I mount that giant game wheel behind my easy chair, I'm traveling back in time with a battery operated printer and mock that Chinese guy when he unveils movable type.Nice. :p

Pff, this is obviously the work of time traveling scientests who found out that the invention of time travel was a horrible idea that unleashed a blight on humanity so they went back in time to establish that time travel wasn't possible so that it would never be invented and thus save the universe.

It's soooo obvious. I ain't buyin' it, as soon as I mount that giant game wheel behind my easy chair, I'm traveling back in time with a battery operated printer and mock that Chinese guy when he unveils movable type.

I wonder what would happen if one went back in time and nuked Rome back when the Senate was still in charge...

I wonder what would happen if one went back in time and nuked Rome back when the Senate was still in charge...

There is only one possible result for the year 2007, if one were to go back in time and do such a thing. Bunnies would become carnivorous. It is so simple to come to this conclusion that it makes me question if you think before typing. Harder questions, please.

There is only one possible result for the year 2007, if one were to go back in time and do such a thing. Bunnies would become carnivorous. It is so simple to come to this conclusion that it makes me question if you think before typing. Harder questions, please.

What? What makes you think they aren't? Suggesting they need to "become" carnivorous is so impossibly stupid that it makes me question if you think before typing.

I'm not sure about this.

How is this new? You can only travel to a physical place... times are not physical places therefore you can't travel to them... However if the theory of multi-verse is in fact, fact....

Olmedreca;12422657']This forum is perfect example of working time travel.:D

They've obviously never been here.

How is this new? You can only travel to a physical place... times are not physical places therefore you can't travel to them... However if the theory of multi-verse is in fact, fact....

That's not really accurate. If time is a dimension, you should be able to change the speed at which you move in that dimension, and reverse it in some way. We know there's no way to actually turn around and go back in time without the use of a wormhole.

However, going forward in time faster or slower than other things is not only feasible, it's been tested. Read up on Time Dilation.

Basically if you stay in an area that has a significantly higher force of gravity than another area (for instance, the area outside a black hole as opposed to our solar system) time for you will physically go slower than time elsewhere. You'll have slowed down your local time flow to the point where if you were to leave the area around the black hole and go back to our solar system, the time different would be phenomenal.

Yea but who will decide who is a "reality deviant", and who is not? George W? God forbid!!!!!!

I couldn't tell you; presumably, it's going to be one government or another. After all, if time travel were accessible to the average person it would be accessible to criminals as well.

Plus, you win the thread if you know what RPG that term comes from.

Getting a Spacetime Hole Puncher would sort humanity pretty permanently. It'd be kind of like "Feck the universe is gonna end next week." "Alright, everyone through the hole, you know the drill"

That's my guess. Eventually, when the time comes we'll have to escape to somewhere else in order to continue our species; one can only wonder what the inhabitants of that universe will do when we arrive. Perhaps they'll call us Gods...

I mean, we've got 100 trillion years to do it so there's no need to panic just yet.

I've heard before that no (hypothetical) time machine could take you back in time to before the machine itself existed.

Can't remember why. Science™, probably.

If we view time as a dimension, much like space, we can view traveling through time as moving through a dimension. Much like anything, moving through any dimension takes force applied to an object generating motion. Whether it is through space or through time, the principle is the same.

Now also presumably since we are moving in a dimension "through time" the flow of time forces us in one direction. To move backwards in time, you must overcome that force.

The theory behind what you are saying is that any machine to make you travel "through time" would be exerting some sort of force on you to move you through. The idea is that you can not have a machine exerting force upon you before it exists.

Imagine sitting in a fast moving stream trying to push a ball upstream. You can exert force on the ball and move it against the current, but once you stop moving (IE before the point where the machine exists) the ball stops with you, and gets carried back on the stream again.

Well, I know shit about physics, but I know about chemistry, and I do know matter doesnt reproduce itself.

Well, actually that's not so certain. Honestly, we don't really have a good idea where matter came from in the first place since we're presently incapable of knowing anything that happened before the Big Bang. The origins of it are still pretty much a mystery so far.

I see the idea of multiple universes as quite stupid. That is wishfull thinking. Or that there are infinite earths and that every nanosecond we go from one to the other, and that if you want to go back in time you just need to "transport" yourself to another universe/earth that exists in a time much more less developed than yours.

Not really, it's actually a pretty common interpretation of the modern physical sciences; it helps explain a lot of the weirdness in quantum theory and does have some pretty solid underpinnings. As a matter of fact, some new observational tests being developed for string theory might enable us to "see" those other universes as part of the experiments being run to test the theory.

Worm holes and black holes that take you to the past or future sounds like a lot of shit to me.

We won't know for sure exactly what's going on until we've made some more advances in the field. They're mathematically and physically possible, so I wouldn't rule them out until they're tested.

No, but I'd sure like to! :D
As soon as I have the chance I'm buying more books about physics, especially covering that first subject. At the moment the only moderately serious book I own is Professor Stephen Hawking's 'A Brief History of Time', and thus I am forced to resort to the ever-unreliable internet for more knowledge.
Also, I have far too many Terry Pratchett books on my shelves. I need some way to let people know that I'm not stalking him.
Studying aspects of quantum physics would probably do the trick.

Ilaer

read "black holes and baby universes" by Hawking

That's not really accurate. If time is a dimension, you should be able to change the speed at which you move in that dimension, and reverse it in some way. We know there's no way to actually turn around and go back in time without the use of a wormhole.

However, going forward in time faster or slower than other things is not only feasible, it's been tested. Read up on Time Dilation.

Basically if you stay in an area that has a significantly higher force of gravity than another area (for instance, the area outside a black hole as opposed to our solar system) time for you will physically go slower than time elsewhere. You'll have slowed down your local time flow to the point where if you were to leave the area around the black hole and go back to our solar system, the time different would be phenomenal.

Thats not really "time travel" then is it? Its sitting in one place not traveling at all...

That's not really accurate. If time is a dimension, you should be able to change the speed at which you move in that dimension, and reverse it in some way. We know there's no way to actually turn around and go back in time without the use of a wormhole.

However, going forward in time faster or slower than other things is not only feasible, it's been tested. Read up on Time Dilation.

Basically if you stay in an area that has a significantly higher force of gravity than another area (for instance, the area outside a black hole as opposed to our solar system) time for you will physically go slower than time elsewhere. You'll have slowed down your local time flow to the point where if you were to leave the area around the black hole and go back to our solar system, the time different would be phenomenal.


But time dilation is not really "traveling through time". Or at least, it's not traveling through time any more so than normal travel through time is travel through time.

The flow of time is merely relative. If you and I start somewhere and go 1 mile away, if you jog and I walk, you will get there faster than me. However you did not move from point A to point B instantaniously, you just did it faster. Our speeds were relative, you moved faster than me

But time dilation is not really "traveling through time". Or at least, it's not traveling through time any more so than normal travel through time is travel through time.

The flow of time is merely relative. If you and I start somewhere and go 1 mile away, if you jog and I walk, you will get there faster than me. However you did not move from point A to point B instantaniously, you just did it faster. Our speeds were relative, you moved faster than me

Agreed... its all a battle of words and the meanings of words... :D

Thats not really "time travel" then is it? Its sitting in one place not traveling at all...

as I said, it's not so much "time travel" as it is simply being in a place where time travels at a different speed. Time is relative. You aren't "traveling through time" when you do this any more than I am traveling through time normally.

At best you are simply traveling faster

You're still thinking in terms of a 3d space. You're constantly MOVING in time. To say that weren't moving in time would mean that you had been frozen in a single instant. So if you're moving in time, you can change the rate at which you move in time, based on Special Relativity.

But we aren't stuck in time that would be the problem... time moves past us... and even then it sounds like a matter of just "moving" faster on this conveyor belts of sorts... not traveling to a place called time.. just moving faster or slower...

Thats not really "time travel" then is it? Its sitting in one place not traveling at all...

You're still thinking in terms of a 3d space. You're constantly MOVING in time. To say that weren't moving in time would mean that you had been frozen in a single instant. So if you're moving in time, you can change the rate at which you move in time, based on Special Relativity.

But time dilation is not really "traveling through time". Or at least, it's not traveling through time any more so than normal travel through time is travel through time.

The flow of time is merely relative. If you and I start somewhere and go 1 mile away, if you jog and I walk, you will get there faster than me. However you did not move from point A to point B instantaniously, you just did it faster. Our speeds were relative, you moved faster than me

But in relation to him you would be in the past; suppose we have point A as the beginning and point Z as the end and that he goes twice as fast as you.
When he gets to point Z you will be around point N, which he has already passed through; you are existing in a past state to him.

And in any case, if he were to instantaneously move to Z then he would be moving faster than you; an infinite percentage of your speed, in fact, as long as you were limited to a finite speed and thus did not also move instantaneously.

Ilaer

Edit: Hey, according to the bit under my user name I'm 'Quite Deadly'. Yay!

But we aren't stuck in time that would be the problem... time moves past us... [QUOTE]

It is perhaps more appropriate that WE are moving THROUGH time. Like walking down the street.

[QUOTE]and even then it sounds like a matter of just "moving" faster on this conveyor belts of sorts... not traveling to a place called time.. just moving faster or slower...

Correct, the speed at which one moves through time is relative. One can influence things such that he moves faster in time than someone else, but that is simply a matter of moving faster or slower.

I found my theory!
Now to have you all tear it to pieces...

I will post in its original form as a post on another forum.
I also include some thoughts from other posters and my refining of the idea.
(Akria is my general internet and forum name; NSG is special because here I'm Ilaer. :D)

I came up with this the other day, asked everyone I could think of about it, including my physics teacher, and no-one could tell me whether or not it was an ok theory...

My physics teacher even told me that I should ask a university lecturer and that it was the sort of thing that impressed them. That's a good thing to know, but it'd be even better to know its feasibility...

Anyway...
Here it is:
Consider the old analogy of the Universe/spacetime as a rubber sheet and matter as a lead weight.
This doesn't really work very well, in my opinion. For one thing, if we think of a model in which spacetime is a solid then it doesn't explain the Cosmological Constant (a statement that spacetime has a built-in tendency to expand, for non-physicists).
Neither does it cope very well with infinitely dense objects, such as black holes; they'd most likely tear a hole in the fabric of spacetime, and I doubt that'd be a good thing (or, indeed, something that we wouldn't notice).
Therefore, my theory attempts to explain both of these by modelling the Universe in a different way.
Consider the Universe as a two dimensional sheet of a very, very viscuous liquid. Now imagine matter as the traditional weight, one which, when place on the sheet of liquid, give it a third dimension (depth).
Thus far we have the rubber sheet model but made out of liquid.
However, I had an idea that the Cosmological Constant could be caused by a process slightly similar to that of diffusion; a liquid allows different concentrations at different areas of the sheet. We could then argue that the Cosmological Constant exists because spacetime is attempting to get a uniform concentration; this would cause expansion in the Universe.
It also allows slightly better for things such as singularities: it's not torn apart but keeps increasing in depth at the location of the singularity.

There are probably a hundred reasons why this is a ludicrous theory but I'm tired and I can't fight my own ideas when tired.
So you can for me.

Akria

Other poster wrote:
Very interesting Akria. Physics makes my brain hurt at the best of times but i will try and throw in some thoughts.

1. Surely any model will be imperfect as it is just that - a model. But thinking of a liquid rather than solid rubber sheet would seem to add a degree of relaism as the liquid has a built in tendancy to expand. However it is still 2 dimensional, and by its very nature is spacetime not 4 dimensional?

2. Why should black holes not rip a hole in the fabric of spacetime? Is this not the theory of space folding, where the rip provides a short path between two distant locations?

3. I like your idea of diffusion. Presumably spacetime under this model would have a 'minimum concentration' as it would eventually find equilibrium between the gravitational forces of matter in the universe stopping it 'spreading' further? However would it not suggest the state of the universe would then be static neither reversing the process leading to the big crunch nor expanding further?

4. Your new model would indeed mean a singularity would simply increase 'depth' and not rip a hole (presumably until it could no longer increase in depth - i guess shown in your model by a 1 molecule think side to the 'hole'). At this point would it tear a hole or would it get deeper but the rest of the universe start contracting and collapsing into the singularity. If this is the case then we all have a bright future to look forward to.

I hope there might be a scrap of useful thoughts there for you to play with!


1. True, but we tend to simplify it as being three-dimensional. I simplified it further as being two-dimensional in its default state and then being three-dimensional once you began to add matter.

2. I hate to think what the rip would really provide... I mean, think about the dangers inherent in ripping a hole in a spaceship's hull. Could it be that a vacuum is in fact something (actually, it almost certainly is something, most likely many anti-matter and matter particles colliding with one another all the time; otherwise we'd be defying Heisenberg's Uncertainty Principle as it applies to a field) and it would then be sucked out into the void outside spacetime? I'm sure you can come up with as many terrifying scenarios as I can.

3. Interesting point. We are then led to one of two things: either my model is wrong and needs adjusting to allow for the possibility of continual expansion (no idea how) or, if my model is correct, then continual expansion is a load of rubbish. You can make your own choice.

4. I believe it would probably continue and begin dragging in the rest of the Universe. However, I don't know what effect it would have; it could just end up that our model keeps dragging itself down and into a deep well but we don't notice a thing.

I think personally the biggest problem with my model is 2.; any suggestions to improve it would be most welcome.

Akria


I refined my original theory and came up with this:

To allow for an easily understandable model that still incorporates time, the fourth dimension, we can take my original as a base and do the following: we make a tower out of the models.

No, really. We have the Universe as it was at the beginning at the bottom, and at each point when time moves on we have, just above it, another model of the Universe at that point, and above that the Universe an instant later, and after that... and so on and so forth.
We allow a very small distance between these on the vertical axis, so as not to allow ordinary matter to affect time.
However, as a singularity would cause a very deep pit as was discussed earlier, it would sink into the previous model which, at the point of the singularity itself is sinking into the one before that, and so on, with the depth of the pit decreasing the further down the tower (and thus closer to the beginning of time) one gets.
This will in effect cause a singularity to exist in the present and the past simultaneously, which I believe could explain the strange effect a singularity has on time as it would be more deeply immersed in the past than the present and thus would show the past more readily than the future.

Thoughts?
I can probably draw a diagram for it if it makes it any clearer, as I know I explained it quite badly.

Akria

There you have it. My model of the Universe with some interesting implications for time travel (in a way) should it work.

Ilaer

your first problem is the assumption that a black hole has infinite density. This is not the case.

It has an extremely high density, but not an infinite one. To be infinite it would need either a infinite mass, or an infinitly small volume. Since we know a black hole is made through a compressed start, it has a finite mass. Likewise it can not be compressed into an infinitly small space.

So a black hole does not have infinite mass, it does, however, have an extremely high mass. So high as to distort space to the point where physical laws break down.

your first problem is the assumption that a black hole has infinite density. This is not the case.

It has an extremely high density, but not an infinite one. To be infinite it would need either a infinite mass, or an infinitly small volume. Since we know a black hole is made through a compressed start, it has a finite mass. Likewise it can not be compressed into an infinitly small space.

So a black hole does not have infinite mass, it does, however, have an extremely high mass. So high as to distort space to the point where physical laws break down.

Technically one needs only an infinitesimally small mass to become a singularity, as I am so keen on pointing out to people.
In any case, this is hardly a major flaw in the theory; a minor inaccuracy, perhaps.
Certainly such a high density would still cause a deep and possibly ever-growing depression in spacetime.

Ilaer

your first problem is the assumption that a black hole has infinite density. This is not the case.

It has an extremely high density, but not an infinite one. To be infinite it would need either a infinite mass, or an infinitly small volume. Since we know a black hole is made through a compressed start, it has a finite mass. Likewise it can not be compressed into an infinitly small space.

So a black hole does not have infinite mass, it does, however, have an extremely high mass. So high as to distort space to the point where physical laws break down.

Actually, the nature of a singularity is that the mass of the original star is compressed into an infinitesimally small space. This is what creates that huge density. The larger space that we associate with the conceptual images of black holes that we have is the extent of the event horizon, which extends around the singularity in a space dictated by its mass.

You Can't Travel Back in Time, Scientists Say
Yay!

Actually, the nature of a singularity is that the mass of the original star is compressed into an infinitesimally small space. This is what creates that huge density. The larger space that we associate with the conceptual images of black holes that we have is the extent of the event horizon, which extends around the singularity in a space dictated by its mass.

I was taught that it had a surface area and volume of 0, thus giving it infinite density.
It is stated that nothing can escape from the pull of a black hole; do we extend this to objects that can move faster than light? If so then a singularity must have infinite density to create truly infinite space-time curvature; otherwise it would be theoretically possible for a sufficiently fast object to escape.

Ilaer

Yay!

That's a bad thing. It means we are doomed no matter what we do.

Ilaer

Actually, the nature of a singularity is that the mass of the original star is compressed into an infinitesimally small space. This is what creates that huge density. The larger space that we associate with the conceptual images of black holes that we have is the extent of the event horizon, which extends around the singularity in a space dictated by its mass.

that's just it, it's not INFINTESIMALLY small.

VERY VERY VERY VERY small yes, but not infintesimally small.

I was taught that it had a surface area and volume of 0, thus giving it infinite density.
It is stated that nothing can escape from the pull of a black hole; do we extend this to objects that can move faster than light? If so then a singularity must have infinite density to create truly infinite space-time curvature; otherwise it would be theoretically possible for a sufficiently fast object to escape.

Ilaer

It's kind of a moot question as nothing can move faster than light and still retain mass. Moreover you have real issues observing particles that move faster than light.

Nothing can escape an event horizon of a black hole because, by definition no THING can move faster than light.

So this means NERVUN is actually going to have to pay the fines on those long-overdue library books, huh?
<_< >_> Uh, I don't know what you mean...

that's just it, it's not INFINTESIMALLY small.

VERY VERY VERY VERY small yes, but not infintesimally small.

I've never heard of a theoretical limit to how small something can become, especially under the force of its own gravity.

In regards to your post after the one I quoted (Jolt was playing up so I was unable to see it before this post):
No? If we had access to an infinite source of energy then we could, I do believe. The problem with making an object move faster than light is that as it approaches light-speed its mass grows to infinity; however, it still has mass and is still thus an object. If one could pour an infinite amount of energy into the acceleration then one could theoretically push it past the light-speed mark.
The observation of such an object is unnecessary; we can observe its effect on other objects more easily.

Ilaer

Just because we can't do it currently doesn't mean it isn't possible, scientist have said that about alot of things that we now do, and take for granted in doing so. Even so I hope we will never discover how to travel in time, can you imagine a dictator or a terrorist that can travel back in time? :eek:

*future me steps into this present time thread from 20 years in the future wearing black round glasses and wearing an outfit a dictator would wear*

Future me: Mwuahahahahahahahahaha.....*glares*

True enough. It hurts my head to think about it.

Theoretically "they" could go do some tinkering and inadvertantly set in motion a chain of events that would end with you never being born. :eek:

Like in that one episode of Red Dwarf with the inquisitor?:eek:

*future me steps into this present time thread from 20 years in the future wearing black round glasses and wearing an outfit a dictator would wear*

Future me: Mwuahahahahahahahahaha.....*glares*

Shhhh! We're having a debate about physics here!
*pushes away gently*

Ilaer

Hey guys? Remember the Red Dwarf episode with all the time jolts or whatever that gave the crew aboard Red Dwarf glimpses of the future? :D

Old Lister: I am you...I mean you are me...Err.. I know your there Lister because when I was your age I remember seeing me at my age telling you...what I'm about to tell you now...

Shhhh! We're having a debate about physics here!
*pushes away gently*

Ilaer

Future me: All that will transpire will do so according to my plan....MWUAHAHAHAHAHAHAHAHA!!!!!!! *imperial march plays from other side of wormhole* Dude! Keep it down General! *shoots into the wormhole* *hears thuds from other side*

Hey guys? Remember the Red Dwarf episode with all the time jolts or whatever that gave the crew aboard Red Dwarf glimpses of the future? :D

Old Lister: I am you...I mean you are me...Err.. I know your there Lister because when I was your age I remember seeing me at my age telling you...what I'm about to tell you now...

I wish I was able to watch Red Dwarf more often... :(

Future me: All that will transpire will do so according to my plan....MWUAHAHAHAHAHAHAHAHA!!!!!!! *imperial march plays from other side of wormhole* Dude! Keep it down General! *shoots into the wormhole* *hears thuds from other side*

Perhaps so if not for...
SUPER PHYSICISTS!

One of whom is now tired and is going to sleep.
See you all tomorrow.

Ilaer

Has anyone here read A Sound of Thunder?

Let me say what I think of this as a n00b in science (compared to what i see of you guys):

We haven't even thought of the time-paradoxes that will occur when timetraveling. Like meeting yourself or killing your father or stuff like that. Will the whole universe collapse when stuff like that happens? Or is it simply not possible.

Ilaer: When I read your model, I see only a model for visualising your vision on time seen from outside the model where the laws of time occur. You can compare this with looking at a flat earth/world from out of the sky. But whatever your model looks like, I think it is irrelevant. For you have chosen time as a fourth dimension. Why not the 5th, 9th or 42th?
Your idea of constructing that tower is actualy not a bad idea. In math the way to draw things in 4D are by constructing their iso-lines (hmm sorry don't know the proper english word for 'isohoogtelijnen'), like you can see at maps that show altitudes. Only there a 2D-image is used to show a 3D-image.
Anyway I'm getting a bit offtopic.
I think what you have done here is creating a model to visualise a 4dimensional object, where time is the fourth dimension. Which isn't far of from mathemathical existing models for a 4D-space, but only with adaptions for time being the 4th dimension.

I just don't think your model is going to help anything. For something you said yourself:
The observation of such an object is unnecessary; we can observe its effect on other objects more easily.
Don't try to look at it from the outside. Observe it from the inside. There is proof that 2D-creatures can, by doing some good mapping, from the inside discover how their world looks like seen from a 3D-space. I think we must do the same concidering the 4th dimension.

I have spoken (in poor English, sorry I'm from Holland)

Has anyone here read A Sound of Thunder?

Yeah, and that's why time travel would probably not be the wisest idea. If you want to have a different timeline, create a new universe instead.

Yeah, and that's why time travel would probably not be the wisest idea. If you want to have a different timeline, create a new universe instead.

Yeah, but then we'd have some dickhead create a personal universe, make a Lavos machine, and terrorise the cosmos...

...Until some spikey-haired kid and his crew take up the challenge and kick his ass. Stupid Lavos.

That's a bad thing. It means we are doomed no matter what we do.

Ilaer

:eek: Doomed to what?

What? What makes you think they aren't? Suggesting they need to "become" carnivorous is so impossibly stupid that it makes me question if you think before typing.

I have dishonoured myself before NS. *commits seppuku*

The way this forum posting works here is evidence of time travel.

I couldn't tell you; presumably, it's going to be one government or another. After all, if time travel were accessible to the average person it would be accessible to criminals as well.

Plus, you win the thread if you know what RPG that term comes from.


Yea after all we all know that there aren't any criminal types allowed in the governments of the world.

It's kind of a moot question as nothing can move faster than light and still retain mass. Moreover you have real issues observing particles that move faster than light.

Nothing can escape an event horizon of a black hole because, by definition no THING can move faster than light.


So we need to transform our bodies into something without mass in order to not break that law.